This invention relates to refrigerated cases, primarily supermarket-type display cases, using air defrost concepts. More particularly, it relates to a system wherein the cooling assembly, or a portion thereof, is exposed to the warmer ambient air in the store for defrosting.
In refrigerators, and particularly in those used in commercial establishments for storing and displaying goods for sale to customers, there is a need to defrost the coils used in the refrigeration system quickly and efficiently. It is especially advantageous that this occur without defrosting the entire refrigerator, as such defrosting could have an adverse affect on the goods being stored and displayed therein. Refrigerators heretofore have included apparatus for introducing ambient air into the refrigeration circuit which will, of course, ultimately defrost the coils. See, e.g., U.S. Pat. No. 3,403,525 (Beckwith et al.); and U.S. Pat. No. 3,648,482 (Beckwith et al.). A problem with this approach, especially in frozen food cases, is that the ambient air flowing through the (normally refrigerated) air flow conduits may cause the goods being displayed to thaw sufficiently to damage the goods. Also, in open front cases, the (normally refrigerated) primary band air curtain may be cut off allowing entry of warmer ambient air into the display/storage section. See, e.g. U.S. Pat. No. 3,850,003 (Beckwith et al) and U.S. Pat. No. 4,026,121 (Aokage et al). All these situations serve to increase the load on the refrigeration unit in bringing the refrigerator back to its normal cooling/freezing temperature.
Approaches to overcome this problem have included changing the flow paths within the refrigeration system so that the ambient air introduced will not pass through portions of the refrigerator adjacent the goods being displayed. See, e.g., U.S. Pat. No. 3,082,612 (Beckwith). In addition, there have been apparatus including door means and cooling coils which are movable out of the flow path of the air and exposed in a way that ambient air being drawn through the coils will not pass through the refrigeration unit. An example of this type of refrigerator is shown in U.S. Pat. No. 2,433,655 (di Zoppola). The di Zoppola device relates to a low temperature cabinet having a hinged door along the top of the cabinet with the coils and fan secured thereto. When it is desired to defrost the coils, the door is pivoted out of the refrigeration cavity to a position where it is readily exposed to the atmosphere for drawing ambient air through the coils to defrost them. To keep the goods within the refrigerator from being exposed to the ambient atmosphere, a separate temporary cover or door is placed across the opening when the door containing the coils and fan is opened during defrost.
Another example of approaches to overcome the defrosting problem is shown in U.S. Pat. No. 2,525,868 to Corhanidis which discloses a refrigeration system having coils adapted to be defrosted by ambient air when a hinged door to the refrigeration unit is open. In this device, a series of shutters are used to change the flow path within the refrigerator so that the ambient air is not drawn into the cavity supporting the refrigerator goods during the defrosting operation. The Corhanidis device however, is one which is relatively complex in operation requiring a sophisticated system interacting with the door to change the flow path.
It is an object of the subject invention to overcome the difficulties in defrosting refrigerators, particularly those used in commercial establishments, which have characterized the refrigerators heretofore.
It is also an object to more efficiently withdraw the coils and fan used in refrigeration systems from the flow path of the refrigerator case and expose this apparatus to the surrounding atmosphere where the ambient air can readily be drawn through the coils without adversely affecting the goods being stored in the refrigerator.
It is another object to provide a system which automatically moves a door having a fan and coil attached thereto into an open position where it is exposed to the ambient air for defrosting the coils without unduly raising the temperature of the cabinet during the defrosting process.
It is still another object to automatically close the air flow path to the plenum chamber normally occupied by the coils and fan when they are moved out of the plenum chamber for defrosting, to thereby prevent the cold air from being drawn out of the refrigeration system during the defrosting process.
It is still a further object to be able to readily expose the fan and coils of the refrigeration unit so that regular maintenance or other repair tasks can be easily accomplished.